Method and apparatus for conducting Raman spectroscopy

ABSTRACT

In another form of the present invention, there is provided a Raman probe comprising: a first optical fiber for receiving laser excitation light from a light source and transmitting the same; a first filter for receiving light from the first optical fiber and adapted to pass the laser excitation light and to block spurious signals associated with the light; a second filter for receiving light from the first filter and adapted to direct the light toward the specimen; focusing apparatus for receiving the light from the second filter, focusing the light on a specimen so as to generate the Raman signal, and returning the Raman signal to the second filter; wherein the second filter is further configured so that when the second filter receives the Raman signal from the focusing apparatus, the second filter filters out unwanted laser excitation light before directing the Raman signal to a second optical fiber; and a second optical fiber for receiving the Raman signal from the second filter and transmitting the same to a light analyzer. In another form of the present invention, there is provided a Raman probe comprising: a light source for generating laser excitation light; focusing apparatus for receiving the laser excitation light from the light source, focusing the laser excitation light on a specimen so as to generate the Raman signal, and returning the Raman signal to a light analyzer; and a light analyzer for analyzing the Raman signature of the specimen, whereby to identify the specimen; wherein the focusing apparatus is configured to permit the specimen to reside in a vial receptacle or at a target location remote from the vial receptacle. In another form of the present invention, there is provided a method for conducting Raman spectroscopy of a specimen, comprising: generating laser excitation light using a light source; passing the laser excitation light through a first filter so as to block spurious signals associated with the light; passing the laser excitation light through a second filter so as to direct the light toward the specimen; receiving the light from the second filter, focusing the light on a specimen so as to generate the Raman signal, and returning the Raman signal to the second filter; wherein the second filter is further configured so that when the second filter receives the Raman signal from the specimen, the second filter filters out unwanted laser excitation light; passing the filtered light received from the second filter to a light analyzer; and analyzing the Raman signature of the specimen so as to identify the specimen. In another form of the present invention, there is provided a Raman probe comprising: a housing; a light source disposed within the housing for generating laser excitation light; focusing apparatus disposed within the housing for receiving the laser excitation light from the light source, focusing the laser excitation light on a specimen so as to generate the Raman signal, and returning the Raman signal to a light analyzer; and a light analyzer disposed within the housing for analyzing the Raman signature of the specimen, whereby to identify the specimen; wherein the focusing apparatus is configured to permit the specimen to reside at a target location remote from the housing; and further comprising an optical shield mounted to the housing so as to be disposed between the specimen and the user, whereby to optically shield the user from the light source. In another form of the present invention, there is provided a Raman probe comprising: a housing; a light source disposed within the housing for generating laser excitation light; focusing apparatus disposed within the housing for receiving the laser excitation light from the light source, focusing the laser excitation light on a specimen so as to generate the Raman signal, and returning the Raman signal to a light analyzer; and a light analyzer disposed within the housing for analyzing the Raman signature of the specimen, whereby to identify the specimen; wherein the focusing apparatus is configured to permit the specimen to reside at a target location remote from the housing; and further comprising a camera mounted to the housing so that its field of view encompasses the target location, and a display mounted to the housing for displaying the image captured by the camera, whereby to permit the user to position the probe relative to the specimen while watching the display.

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

This patent application claims benefit of:

-   -   (i) pending prior U.S. Provisional Patent Application Ser. No.        60/566,713, filed Apr. 30, 2004 by Peidong Wang et al. for RAMAN        SPECTROSCOPY TECHNIQUES OVER OPTICAL FIBERS (Attorney's Docket        No. AHURA-22 PROV); and    -   (ii) pending prior U.S. Provisional Patent Application Ser. No.        60/607,735, filed Sep. 7, 2004 by Kevin Knopp et al. for RAMAN        PROBE WITH INLINE VIAL CAPABILITY (Attorney's Docket No.        AHURA-30 PROV).

The two above-identified patent applications are hereby incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to methods and apparatus for identifying andcharacterizing substances in general, and more particularly to methodsand apparatus for identifying and characterizing substances using Ramanspectroscopy.

BACKGROUND OF THE INVENTION

Raman spectroscopy is a viable technique for identifying andcharacterizing a vast array of substances. Raman spectroscopy is widelyused in both the scientific and commercial areas. By way of example butnot limitation, commercial areas of use currently include medicine,biotechnology, pharmaceuticals, security and geology. In addition,recent technological advances are making it possible to increase therange of applications using Raman spectroscopy through a reduction incost and size. For example, portable units have recently becomeavailable for out-of-lab uses such as the measurement and identificationof powders, pills, liquids, etc.

Unfortunately, a number of problems exist with respect to current Ramanspectroscopy systems. For example, a persistent problem in existingRaman spectroscopy systems is the delivery of laser light to thespecimen and the collection of the Raman signature from the specimen.Among other things, these problems include space limitations in portableRaman systems, signal distortions introduced into the system due toAmplified Spontaneous Emission (ASE) from the laser sources, etc.

Also, for Raman spectroscopy of specimens which are located remotelyfrom the light sources and light detectors, optical fibers are commonlyused to deliver the excitation light and to collect the Raman signals.However, the use of these optical fibers can introduce fluorescence andRaleigh and Raman scatterings generated through interactions in theoptical fibers.

Accordingly, a primary object of the present invention is to provide animproved Raman spectroscopy system which overcomes the shortcomings ofcurrently available systems.

SUMMARY OF THE INVENTION

In one preferred embodiment of the present invention, there is providedan improved Raman spectroscopy system (sometimes hereinafter referred toas a Raman probe) in which a set of optical elements is used to separatethe pump source from the Raman signal and to direct the Raman signal toa remote spectrometer or detector. The Raman probe is preferably alsoconfigured so as to be able to filter ASE background from the lasersources, as well as to filter fluorescence and Raleigh and Ramanscatterings generated through interactions in the optical fibers.

In another form of the present invention, there is provided a Ramanprobe comprising:

-   -   a first optical fiber for receiving laser excitation light from        a light source and transmitting the same;    -   a first filter for receiving light from the first optical fiber        and adapted to pass the laser excitation light and to block        spurious signals associated with the light;    -   a second filter for receiving light from the first filter and        adapted to direct the light toward a specimen;    -   focusing apparatus for receiving the light from the second        filter, focusing the light on the specimen so as to generate the        Raman signal, and returning the Raman signal to the second        filter;    -   wherein the second filter is further configured so that when the        second filter receives the Raman signal from the focusing        apparatus, the second filter filters out unwanted laser        excitation light before directing the Raman signal to a second        optical fiber; and    -   a second optical fiber for receiving the Raman signal from the        second filter and transmitting the same to a light analyzer.

And in one preferred embodiment of the invention, a novel optical probedelivery system is provided which offers three unique modes of use forexciting and collecting light from the specimen under test, allencompassed with one optical probe design. In a first mode of use, theRaman probe allows the user to maintain distance from the specimen byusing a conical standoff, which provides both distance control and lasersafety by limiting the exposed beams. The second mode of use allows theuser to remove the conical standoff so as to maintain distance controlby hand or other means. The third mode of use allows a specimen vial tobe inserted directly within the probe optics assembly.

In another form of the present invention, there is provided a Ramanprobe comprising:

-   -   a light source for generating laser excitation light;    -   focusing apparatus for receiving the laser excitation light from        the light source, focusing the laser excitation light on a        specimen so as to generate the Raman signal, and returning the        Raman signal to a light analyzer; and    -   a light analyzer for analyzing the Raman signature of the        specimen, whereby to identify the specimen;    -   wherein the focusing apparatus is configured to permit the        specimen to reside in a vial receptacle or at a target location        remote from the vial receptacle.

In another form of the present invention, there is provided a method forconducting Raman spectroscopy of a specimen, comprising:

-   -   generating laser excitation light using a light source;    -   passing the laser excitation light through a first filter so as        to block spurious signals associated with the light;    -   directing the laser excitation light to a second filter so as to        direct the laser excitation light toward the specimen;    -   receiving the light from the second filter, focusing the light        on the specimen so as to generate the Raman signal, and        returning the Raman signal to the second filter;    -   wherein the second filter is further configured so that when the        second filter receives the Raman signal from the specimen, the        second filter filters out unwanted laser excitation light;    -   passing the filtered light received from the second filter to a        light analyzer; and    -   analyzing the Raman signature of the specimen so as to identify        the specimen.

In another form of the present invention, there is provided a Ramanprobe comprising:

-   -   a housing;    -   a light source disposed within the housing for generating laser        excitation light;    -   focusing apparatus disposed within the housing for receiving the        laser excitation light from the light source, focusing the laser        excitation light on a specimen so as to generate the Raman        signal, and returning the Raman signal to a light analyzer; and    -   a light analyzer disposed within the housing for analyzing the        Raman signature of the specimen, whereby to identify the        specimen;    -   wherein the focusing apparatus is configured to permit the        specimen to reside at a target location remote from the housing;    -   and further comprising an optical shield mounted to the housing        so as to be disposed between the specimen and the user, whereby        to optically shield the user from the light source.

In another form of the present invention, there is provided a Ramanprobe comprising:

-   -   a housing;    -   a light source disposed within the housing for generating laser        excitation light;    -   focusing apparatus disposed within the housing for receiving the        laser excitation light from the light source, focusing the laser        excitation light on a specimen so as to generate the Raman        signal, and returning the Raman signal to a light analyzer; and    -   a light analyzer disposed within the housing for analyzing the        Raman signature of the specimen, whereby to identify the        specimen;    -   wherein the focusing apparatus is configured to permit the        specimen to reside at a target location remote from the housing;    -   and further comprising a camera mounted to the housing so that        its field of view encompasses the target location, and a display        mounted to the housing for displaying the image captured by the        camera, whereby to permit the user to position the probe        relative to the specimen while watching the display.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which is tobe considered together with the accompanying drawings wherein likenumbers refer to like parts and further wherein:

FIG. 1 illustrates a novel Raman optical probe;

FIG. 1A illustrates the overall Raman spectroscopy system in schematicform;

FIG. 2 illustrates a thin film design to filter out the ASE,fluorescence and Raleigh and Raman scattering from the fibers;

FIG. 3 illustrates thin films designed for reflective (blocking) laserlines and transmitting Raman signals;

FIG. 4 illustrates an additional broadband reflector to direct Ramansignals and blocking the laser lines;

FIG. 5 illustrates another Raman probe layout where the broadbandreflector is omitted through the rearrangement of collecting fibers;

FIG. 6 illustrates another embodiment of the present invention, whereinthe fibers and signal collecting optics are collinear (as opposed tobeing perpendicular to each other);

FIG. 7 illustrates another embodiment which is similar to that of FIG.1, except using a 5 degree of Angle Of Incidence (AOI) for the filters;

FIG. 8 illustrates another embodiment which is similar to that of FIG.5, except using a 5 degree of Angle Of Incidence (AOI) for the filters;

FIG. 9 illustrates another embodiment which is a variation of FIG. 6,except using a 10 degree AOI for the filters;

FIG. 10 illustrates another embodiment of Raman probe which is designedto be more compact through the use of two prisms with various coatingson the surface;

FIG. 11 illustrates a portable Raman probe which is configured to allowthree different methods of use;

FIGS. 12 and 13 illustrate the portable Raman probe of FIG. 11configured to allow the user to maintain distance from the specimenusing a conical standoff;

FIG. 14 illustrates the portable Raman probe of FIG. 11 configured toallow the user to remove the conical standoff so as to maintain distancecontrol by hand or other means;

FIG. 14A illustrates a novel portable Raman probe with another form ofconical standoff;

FIGS. 15-17 illustrate the portable Raman probe of FIG. 11 configured toallow the user to insert a specimen vial directly within the probeoptics assembly;

FIG. 18 is a schematic view showing a specimen vial inserted directlywithin the probe optics assembly, wherein the specimen vial incorporatesa shutter to prevent stray backlight from entering the vial receptacle;and

FIG. 19 is a schematic view showing a camera mounted to the front of theRaman probe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Novel RamanSpectroscope

Looking first at FIG. 1, there is shown a novel Raman probe 5. Theexcitation light source LS in this arrangement may be, for example, oneor more 785 nm semiconductor lasers with limited linewidths. However,the Raman probe 5 may also use any other laser source as the excitationlight source LS as long as the laser source is compatible with Ramanspectroscopy detection techniques. The output of excitation light sourceLS is delivered through optical fiber 10 and collimated through lens 15.A bandpass filter 20 (or multiple combination of bandpass filters 20A,20B) is used to pass the laser excitation light and to block spurioussignals associated with the laser, the fiber, and/or both. The spurioussignals associated with the laser generally comprise ASE from the laser,and the spurious signals associated with the fiber generally comprisefluorescence and Raleigh and Raman scatterings generated inside thefiber 10. Preferably bandpass filter 20 is adapted to block spurioussignals associated with both the laser and the fiber. The laserexcitation light is then reflected by filters 25 (at a 22.5 degree Angleof Optical Incidence, AOI) and 30 (at a 22.5 degree AOI), and then it isfocused through lens 35 to excite specimen 40. In this respect it shouldbe appreciated that, for the purposes of the present disclosure, certainAOI values are used, however, in accordance with the present invention,the AOI may vary from one embodiment to another. Moreover, since thegeometry of the input fiber and output fiber does not need to beparallel or perpendicular, AOI values may vary with the particulargeometry employed, e.g., the AOI values may be anywhere from 5 degreeAOI to 50 degree AOI. In one preferred embodiment of the presentinvention, filters 25 and 30 are preferably long-pass filters. In thisrespect it should also be appreciated that filter 25 may be replaced bya simple reflector to reflect the laser light. After the laserexcitation light has been projected on the specimen, the Raman signal isre-collimated through lens 35 and passed through filter 30.Alternatively, the Raman signal may pass through multiple filters (i.e.,in addition to passing through filter 30, the Raman signal may passthrough additional filter 45, at a 22.5 degree AOI). In one preferredembodiment of the present invention, additional filter 45 is preferablyalso a long-pass filter. When the Raman signal from the specimen ispassed though filter 30, filter 30 serves a second purpose at this time,i.e., it blocks the laser line. Filters 30 and 45 can provide upto >OD10 filtration of the laser line before the light is redirectedthrough broadband reflector 50 (at a 45 degree AOI) and focus lens 55into collecting optical fibers 60. Optical fibers 60 transmit the Ramansignal to a light analyzer LA which analyzes the Raman signature of thespecimen, whereby to identify the specimen. The light analyzer LA maycomprise a spectrometer with associated analysis apparatus of the sortwell known in the art. See, for example, FIG. 1A, which shows theoverall Raman spectroscopy system in schematic form. In addition toreflecting the Raman signal, broadband reflector 50 also filters outlaser excitation light (OD1).

Dielectric Thin Film Filters

The various filtering described above may be accomplished by thefollowing dielectric thin film filters. In this respect, for thepurposes of the present disclosure, it will be assumed that the Ramansignal of interest is >300 cm−1. Raman signal that is close to theexcitation source (i.e., about 100 cm−1 to about 300 cm−1) can also bedetected through another set of filters.

(1) Passband Filter Design.

As noted above, one or more passband filters 20A, 20B can be used topass the laser light and block spurious signals associated with thelaser, the fiber, and/or both. A passband filter can be constructedusing a dielectric thin film construction. See, for example, FIG. 2,which illustrates the transmission characteristics of a thin film designconfigured to filter out laser ASE, and the fluorescence and Raleigh andRaman scattering in the fibers.

(2) Filter Design.

As also noted above, filters 25, 30 and/or 45 (in one embodiment of theinvention, preferably long-pass filters) can be used to reflect or blockthe laser line and to pass the Raman signals. Such filters can beconstructed using dielectric thin film constructions. The design ispreferably configured for the range of 800 nm-1100 nm; the CCD detectoris generally not sensitive beyond this range. See, for example, FIG. 3,which illustrates the transmission characteristics of a filter thin filmdesign for reflecting (and/or blocking) laser lines and for transmittingRaman signals.

(3) Additional Broadband Reflector.

The additional broadband reflector 50 is used to redirect the Ramansignal to the collecting fibers. In addition, the additional broadbandreflector 50 further filters the laser excitation light (OD>1) beforepassing the light to the collecting fibers. The broadband reflector 50can also be constructed using dielectric thin film constructions. See,for example, FIG. 4, which illustrates the transmission characteristicsof an additional broadband reflector 50 configured to direct Ramansignals and block the laser lines.

Additional Novel Constructions

Looking now at FIG. 5, there is shown another novel Raman probe layout105 which is generally similar in construction to that shown in FIG. 1,except that the broadband reflector 50 is omitted through therearrangement of the collecting fibers. Thus, in the construction shownin FIG. 5, the output of excitation light source LS is delivered throughoptical fiber 110 and collimated through lens 115. A bandpass filter 120(or multiple combination of bandpass filters 120A, 120B) is used to passthe laser excitation light and to block spurious signals associated withthe laser, the fiber, and/or both. The spurious signals associated withthe laser generally comprise ASE from the laser, and the spurioussignals associated with the fiber generally comprise fluorescence andRaleigh and Raman scatterings generated inside the fiber 110. Preferablybandpass filter 120 is adapted to block spurious signals associated withboth the laser and the fiber. The laser excitation light is thenreflected by filters 125 (at a 22.5 degree AOI) and 130 (at a 22.5degree AOI), and then it is focused through lens 135 to excite specimen140. In this respect it should be appreciated that, for the purposes ofthe present disclosure, certain AOI values are used, however, inaccordance with the present invention, the AOI may vary from oneembodiment to another. Moreover, since the geometry of the input fiberand output fiber does not need to be parallel or perpendicular, AOIvalues may vary with the particular geometry employed, e.g., the AOIvalues may be anywhere from 5 degree AOI to 50 degree AOI. In onepreferred embodiment of the present invention, filters 125 and 130 arepreferably long-pass filters. In this respect it should also beappreciated that filter 125 may be replaced by a simple reflector toreflect the laser light. After the laser excitation light has beenprojected on the specimen, the Raman signal is re-collimated throughlens 135 and passed through filter 130. Alternatively, the Raman signalmay pass through multiple filters (i.e., in addition to passing throughfilter 130, the Raman signal may pass through additional filter 145, ata 22.5 degree AOI). In one preferred embodiment of the presentinvention, additional filter 145 is preferably also a long-pass filter.When the Raman signal from the specimen is passed though filter 130,filter 130 serves a second purpose at this time, i.e., it blocks thelaser line. Filters 130 and 145 can provide up to >OD10 filtration ofthe laser line before the light is redirected by focus lens 155 intocollecting optical fibers 160. Optical fibers 160 transmit the Ramansignal to a light analyzer LA which analyzes the Raman signature of thespecimen, whereby to identify the specimen. The light analyzer LA maycomprise a spectrometer with associated analysis apparatus of the sortwell known in the art. See, for example, FIG. 1A, which shows theoverall Raman spectroscopy system in schematic form.

Looking next at FIG. 6, there is shown another novel Raman probe layout205 which is generally similar to the construction shown in FIG. 5;however, with this novel arrangement, the fibers and signal collectingoptics are collinear with one another (rather than being perpendicularto one another). Thus, in the construction shown in FIG. 6, the outputof excitation light source LS is delivered through optical fiber 210 andcollimated through lens 215. A bandpass filter 220 (or multiplecombination of bandpass filters 220A, 220B) is used to pass the laserexcitation light and to block spurious signals associated with thelaser, the fiber, and/or both. The spurious signals associated with thelaser generally comprise ASE from the laser, and the spurious signalsassociated with the fiber generally comprise fluorescence and Raleighand Raman scatterings generated inside the fiber 210. Preferablybandpass filter 220 is adapted to block spurious signals associated withboth the laser and the fiber. The laser excitation light is thenreflected by filters 225 (at a 22.5 degree AOI) and 230 (at a 22.5degree AOI), and then it is focused through lens 235 to excite specimen240. In this respect it should be appreciated that, for the purposes ofthe present disclosure, certain AOI values are used, however, inaccordance with the present invention, the AOI may vary from oneembodiment to another. Moreover, since the geometry of the input fiberand output fiber does not need to be parallel or perpendicular, AOIvalues may vary with the particular geometry employed, e.g., the AOIvalues may be anywhere from 5 degree AOI to 50 degree AOI. In onepreferred embodiment of the present invention, filters 225 and 230 arepreferably long-pass filters. In this respect it should also beappreciated that filter 225 may be replaced by a simple reflector toreflect the laser light. After the laser excitation light has beenprojected on the specimen, the Raman signal is re-collimated throughlens 235 and passed through filter 230. Alternatively, the Raman signalmay pass through multiple filters (i.e., in addition to passing throughfilter 230, the Raman signal may pass through additional filter 245, ata 22.5 degree AOI). In one preferred embodiment of the presentinvention, additional filter 245 is preferably also a long-pass filter.When the Raman signal from the specimen is passed through filter 230,filter 230 serves a second purpose at this time, i.e., it blocks thelaser line. Filters 230 and 245 can provide up to >OD10 filtration ofthe laser line before the light is redirected by focus lens 255 intocollecting optical fibers 260. Optical fibers 260 transmit the Ramansignal to a light analyzer LA which analyzes the Raman signature of thespecimen, whereby to identify the specimen. The light analyzer LA maycomprise a spectrometer with associated analysis apparatus of the sortwell known in the art. See, for example, FIG. 1A, which shows theoverall Raman spectroscopy system in schematic form.

It should be appreciated that with the constructions shows in FIGS. 1-6,the configurations preferably utilize a 22.5 degree Angle of OpticalIncidence (AOI) for filters 25, 30 and/or 45 (or 125, 130 and/or 145,etc.). However, as noted above, any other AOI can also be configured totake advantage of certain manufacturing tolerances.

For example, and looking now at FIG. 7, there is shown another novelRaman probe configuration 305 which uses a different AOI for thefilters. With this construction, the output of excitation light sourceLS is delivered through optical fiber 310 and collimated through lens315. A bandpass filter 320 (or multiple combination of bandpass filters320A, 320B) is used to pass the laser excitation light and to blockspurious signals associated with the laser, the fiber, and/or both. Thespurious signals associated with the laser generally comprise ASE fromthe laser, and the spurious signals associated with the fiber generallycomprise fluorescence and Raleigh and Raman scatterings generated insidethe fiber 310. Preferably bandpass filter 320 is adapted to blockspurious signals associated with both the laser and the fiber. The laserexcitation light is then reflected by a filter 325, which in thisconfiguration may be a laser line reflector (at a 40 degree Angle ofOptical Incidence, AOI) and a filter 330 (at a 5 degree AOI), and thenit is focused through lens 335 to excite specimen 340. In this respectit should be appreciated that, for the purposes of the presentdisclosure, certain AOI values are used, however, in accordance with thepresent invention, the AOI may vary from one embodiment to another.Moreover, since the geometry of the input fiber and output fiber doesnot need to be parallel or perpendicular, AOI values may vary with theparticular geometry employed, e.g., the AOI values may be anywhere from5 degree AOI to 50 degree AOI. In one preferred embodiment of thepresent invention, filter 330 is preferably a long-pass filter. In thisembodiment, laser line reflector 325 is preferably a simple reflector toreflect the laser light. After the laser excitation light has beenprojected on the specimen, the Raman signal is re-collimated throughlens 335 and passed through filter 330. Alternatively, the Raman signalmay pass through multiple filters (i.e., in addition to passing throughfilter 330, the Raman signal may pass through additional filter 345, ata 5 degree AOI). In one preferred embodiment of the present invention,additional filter 345 is preferably also a long-pass filter. When theRaman signal from the specimen is passed though filter 330, filter 330serves a second purpose at this time, i.e., it blocks the laser line.Filters 330 and 345 can provide up to >OD10 filtration of the laser linebefore the light is redirected through broadband reflector 350 (at a 45degree AOI) and focus lens 355 into collecting optical fibers 360.Optical fibers 360 transmit the Raman signal to a light analyzer LAwhich analyzes the Raman signature of the specimen, whereby to identifythe specimen. The light analyzer LA may comprise a spectrometer withassociated analysis apparatus of the sort well known in the art. See,for example, FIG. 1A, which shows the overall Raman spectroscopy systemin schematic form. In addition to reflecting the Raman signal, broadbandreflector 350 also filters out laser excitation light (OD1).

As noted above, Raman probe configuration 305 uses a 5 degree AOI forfilters 330 and 345. Such a small AOI can reduce the s and ppolarization differences which are associated with a large angle of AOI.By using a smaller AOI value, the Raman signal at around ˜300 cm−1 (orsmaller) can be readily resolved. In this configuration, laser linereflector (or filter) 325 is designed for a 40 degree AOI. The laserline reflector 325 may be a simple laser line Distributed BraggReflector (DBR).

It should be appreciated that with a much narrower bandpass filter and afilter with a much smaller AOI, Raman signals as close as 100 cm−1 canalso be readily utilized.

Looking now at FIG. 8, there is shown another novel Raman probeconfiguration 405 which also uses a smaller AOI for the filters (whichare preferably long-pass filters). More particularly, with thisconstruction, the output of excitation light source LS is deliveredthrough optical fiber 410 and collimated through lens 415. A bandpassfilter 420 (or multiple combination of bandpass filters 420A, 420B) isused to pass the laser excitation light and to block spurious signalsassociated with the laser, the fiber, and/or both. The spurious signalsassociated with the laser generally comprise ASE from the laser, and thespurious signals associated with the fiber generally comprisefluorescence and Raleigh and Raman scatterings generated inside thefiber 410. Preferably bandpass filter 420 is adapted to block spurioussignals associated with both the laser and the fiber. The laserexcitation light is then reflected by a laser line reflector 425 (at a40 degree Angle of Optical Incidence, AOI) and a filter 430 (at a 5degree AOI), and then it is focused through lens 435 to excite specimen440. In this embodiment, laser line reflector 425 is preferably a simplereflector to reflect the laser light. In this respect it should beappreciated that, for the purposes of the present disclosure, certainAOI values are used, however, in accordance with the present invention,the AOI may vary from one embodiment to another. Moreover, since thegeometry of the input fiber and output fiber does not need to beparallel or perpendicular, AOI values may vary with the particulargeometry employed, e.g., the AOI values may be anywhere from 5 degreeAOI to 50 degree AOI. In one preferred embodiment of the presentinvention, filter 430 is preferably a long-pass filter. After the laserexcitation light has been projected on the specimen, the Raman signal isre-collimated through lens 435 and passed through filter 430.Alternatively, the Raman signal may pass through multiple filters (i.e.,in addition to passing through filter 430, the Raman signal may passthrough additional filter 445, at a 5 degree AOI). In one preferredembodiment of the present invention, additional filter 445 is preferablyalso a long-pass filter. When the Raman signal from the specimen ispassed a through filter 430, filter 430 serves a second purpose at thistime, i.e., it blocks the laser line. Filters 430 and 445 can provide upto >OD10 filtration of the laser line before the light is redirected byfocus lens 455 into collecting optical fibers 460. Optical fibers 460transmit the Raman signal to a light analyzer LA which analyzes theRaman signature of the specimen, whereby to identify the specimen. Thelight analyzer LA may comprise a spectrometer with associated analysisapparatus of the sort well known in the art. See, for example, FIG. 1A,which shows the overall Raman spectroscopy system in schematic form.

As noted above, any other angles in the filters can also be used toconfigure the Raman probe wherein the fibers and signal collectingoptics are collinear with one another. Thus, in the construction shownin FIG. 9, the output of excitation light source LS is delivered throughoptical fiber 510 and collimated through lens 515. A bandpass filter 520(or multiple combination of bandpass filters 520A, 520B) is used to passthe laser excitation light and to block spurious signals associated withthe laser, the fiber, and/or both. The spurious signals associated withthe laser generally comprise ASE from the laser, and the spurioussignals associated with the fiber generally comprise fluorescence andRaleigh and Raman scatterings generated inside the fiber 510. Preferablybandpass filter 520 is adapted to block spurious signals associated withboth the laser and the fiber. The laser excitation light is thenreflected by filters 525 (at a 10 degree AOI) and 530 (at a 10 degreeAOI), and then it is focused through lens 535 to excite specimen 540. Inthis respect it should be appreciated that, for the purposes of thepresent disclosure, certain AOI values are used, however, in accordancewith the present invention, the AOI may vary from one embodiment toanother. Moreover, since the geometry of the input fiber and outputfiber does not need to be parallel or perpendicular, AOI values may varywith the particular geometry employed, e.g., the AOI values may beanywhere from 5 degree AOI to 50 degree AOI. In one preferred embodimentof the present invention, filters 525 and 530 are preferably long-passfilters. In this respect it should also be appreciated that filter 525may be replaced by a simple reflector to reflect the laser light. Afterthe laser excitation light has been projected on the specimen, the Ramansignal is re-collimated through lens 535 and passed through filter 530.Alternatively, the Raman signal may pass through multiple filters (i.e.,in addition to passing through filter 530, the Raman signal may passthrough additional filter 545, at a 10 degree AOI). In one preferredembodiment of the present invention, additional filter 545 is preferablyalso a long-pass filter. When the Raman signal from the specimen ispassed through filter 530, filter 530 serves a second purpose at thistime, i.e., it blocks the laser line. Filters 530 and 545 can provide upto >OD10 filtration of the laser line before the light is redirected byfocus lens 555 into collecting optical fibers 560. Optical fibers 560transmit the Raman signal to a light analyzer LA which analyzes theRaman signature of the specimen, whereby to identify the specimen. Thelight analyzer LA may comprise a spectrometer with associated analysisapparatus of the sort well known in the art. See, for example, FIG. 1A,which shows the overall Raman spectroscopy system in schematic form.

The Raman probe can also be made significantly more compact by utilizingtwo prisms with various coatings on their surfaces. One such embodimentis illustrated in FIG. 10. In this configuration, the functions of thevarious coatings are the same as discussed above. More particularly, inFIG. 10 there is shown a Raman probe configuration 605. The output ofexcitation light source LS is delivered through optical fiber 610 andcollimated through lens 615. A bandpass filter coating 665 on a firstprism 675 is used to pass the laser excitation light and to blockspurious signals associated with the laser, the fiber, and/or both. Thespurious signals associated with the laser generally comprise ASE fromthe laser, and the spurious signals associated with the fiber generallycomprise fluorescence and Raleigh and Raman scatterings generated insidethe fiber 610. Preferably bandpass filter 620 is adapted to blockspurious signals associated with both the laser and the fiber. The laserexcitation light is then reflected by a dichroic beamsplitter coating680, at a 45 degree AOI, through a broadband AntiReflection (AR) coating670 and then it is focused through lens 635 to excite specimen 640. Inthis respect it should be appreciated that, for the purposes of thepresent disclosure, certain AOI values are used, however, in accordancewith the present invention, the AOI may vary from one embodiment toanother. Moreover, since the geometry of the input fiber and outputfiber does not need to be parallel or perpendicular, AOI values may varywith the particular geometry employed, e.g., the AOI values may beanywhere from 5 degree AOI to 50 degree AOI. After the laser excitationlight has been projected on the specimen, the Raman signal isre-collimated through lens 635 and passed through broadband AR coating670. When the Raman signal from the specimen is passed though broadbandAR coating 670, broadband AR coating 670 serves a second purpose at thistime, i.e., it blocks the laser line. The light passes through secondprism 685, and then through filter coating 690 before being redirectedby focus lens 655 into collecting optical fibers 660. Optical fibers 660transmit the Raman signal to a light analyzer LA which analyzes theRaman signature of the specimen, whereby to identify the specimen. Thelight analyzer LA may comprise a spectrometer with associated analysisapparatus of the sort well known in the art. See, for example, FIG. 1A,which shows the overall Raman spectroscopy system in schematic form.

Portable Raman Probe with Inline Vial Capability

Raman optical probes of the type shown in FIGS. 1-10 may be used fordelivery and collection of light to and from the specimen in a varietyof settings. However, usability challenges can arise when trying toutilize such a Raman optical probe in portable field applications.

By way of example, with the construction shown in FIG. 1, the distancefrom delivery/collection lens 35 and the specimen 40 must generally bekept to within approximately +/−0.5 mm of the focal length of lens 35 soas to maximize the signal strength.

In addition, many users may desire to maintain the specimen 40 close tothe lens 35, while not actually touching the specimen, so as to avoidcontaminating the Raman probe instrument with the specimen.

Also, some users may prefer to have their specimens placed in a glassvial during measurement. This can be awkward with prior art Ramanprobes.

To address these and other concerns, the present invention provides anovel Raman probe which may be used in three different modes of use. Ina first mode of use, the Raman probe allows the user to maintaindistance from the specimen using a conical standoff, which provides bothdistance control and laser safety by limiting the exposed beams. Thesecond mode of use allows the user to remove the conical standoff so asto maintain distance control by hand or other means. The third mode ofuse allows a specimen vial to be inserted directly within the probeoptics assembly.

More particularly, and looking now at FIG. 11, there is shown a novelRaman probe configuration 705 which provides the three aforementionedmodes of use. With this construction, the output of excitation lightsource LS is delivered through optical fiber 710 and collimated throughlens 715. A bandpass filter 720 (or multiple combination of bandpassfilters 720A, 720B) is used to pass the laser excitation light and toblock spurious signals associated with the laser, the fiber, and/orboth. The spurious signals associated with the laser generally compriseASE from the laser, and the spurious signals associated with the fibergenerally comprise fluorescence and Raleigh and Raman scatteringsgenerated inside the fiber 710. Preferably bandpass filter 720 isadapted to block spurious signals associated with both the laser and thefiber. The laser excitation light is then reflected by a laser linereflector 725 (e.g., at a 22.5 degree Angle of Optical Incidence, AOI)and a filter 730 (e.g., at a 22.5 degree AOI), and then it is focusedthrough lens 735 on specimen vial receptacle 805, or passed through thespecimen vial receptacle 805 and through a focus lens 800, and thenthrough another focus lens 795, to a specimen location 740. In thisrespect it should be appreciated that, for the purposes of the presentdisclosure, certain AOI values are used, however, in accordance with thepresent invention, the AOI may vary from one embodiment to another.Moreover, since the geometry of the input fiber and output fiber doesnot need to be parallel or perpendicular, AOI values may vary with theparticular geometry employed, e.g., the AOI values may be anywhere from5 degree AOI to 50 degree AOI. In one preferred embodiment of thepresent invention, filter 730 is preferably a long-pass filter. In thisembodiment, laser line reflector 725 is preferably a simple reflector toreflect the laser light. After the laser excitation light has beenprojected on the specimen, the Raman signal is re-collimated throughlens 735 (where the specimen is located in vial receptacle 805), orlenses 795, 800 and 735 (where the specimen is located at specimenlocation 740) and passed through filter 730. Alternatively, the Ramansignal may pass through multiple filters (i.e., in addition to passingthrough filter 730, the Raman signal may pass through additional filter745 (e.g., at a 22.5 degree AOI). In one preferred embodiment of thepresent invention, additional filter 45 is preferably also a long-passfilter. When the Raman signal from the specimen is passed through filter730, filter 730 serves a second purpose at this time, i.e., it blocksthe laser line. Filters 730 and 745 can provide up to >OD10 filtrationof the laser line before the light is redirected by focus lens 755 intocollecting optical fibers 760. Optical fibers 760 transmit the Ramansignal to a light analyzer LA which analyzes the Raman signature of thespecimen, whereby to identify the specimen. The light analyzer LA maycomprise a spectrometer with associated analysis apparatus of the sortwell known in the art. See, for example, FIG. 1A, which shows theoverall Raman spectroscopy system in schematic form. In one preferredembodiment of the invention, filters 730 and/or 745 may compriselong-pass filters.

The novel Raman probe 705 may be implemented and used as follows.

Looking first at FIGS. 12, 13, 14 and 14A, in the first mode of use, thenovel Raman probe 705 allows the user to maintain distance to thespecimen using a conical standoff 810 which mounts to the housing 815 ofthe Raman probe adjacent to output fiber 760. The conical standoff 810is designed to provide both distance control and laser safety (bylimiting beam exposure). Conical standoff 810 can be manufactured as adisposable element so as to alleviate contamination concerns, or it canbe a more permanent element of the Raman probe. In one preferredconstruction, the probe and conical standoff include a mechanism forattaching and removing a permanent or disposable conical standoff to andfrom a portable Raman unit. Among other things, the conical standoff maybe snap fit to the remainder of the probe (see FIG. 14), or the conicalstandoff may be pivotally attached to the remainder of the probe so thatit may be swung into and out of position as desired.

The conical standoff 810 may comprise a variety of configurations, e.g.,such as those shown in FIGS. 12-14 and 14A. In one preferred form of theinvention, conical standoff 810 comprises an outer cone 810A (FIG. 13)which serves as the distance standoff and an inner cone 810B whichprovides eye safety. Preferably, the inner cone 810B is backpainted toconceal laser light. The conical standoff can be made from plastic ormetal or a combination of the two materials. A glass window 810C (FIG.12) may be provided at the point of laser emission to prevent thespecimen from penetrating into the cone. Optionally, a switch (notshown) in conical standoff 810 may be provided to trigger laser emissionon contact with the sample. If desired, conical standoff 810 maycomprise a half-moon filter 810D (FIG. 14A) surrounding the outerperimeter of outer cone 810A, where the filter elements 810E areconfigured to filter out the operative wavelength of the laser so as toprevent direct viewing of the laser beam and thereby provide operatorsafety.

The second mode of use allows the user to remove the conical standoff810 so as to maintain the desired distance manually or with other means.This mode also allows the user to avoid having to touch the specimenwhich, again, can help alleviate contamination concerns. In this secondmode, it is also possible to couple the use of an electronic/opticalmethod to provide a feedback signal which is proportional to thedistance between the specimen and the lens in order to optimize theRaman signal.

In the third mode of use, and looking now at FIGS. 15-17, a vial 820 maybe inserted in vial receptacle 805 so that the vial 820 sits within theprobe optics assembly. The additional optics permit the light to befocused on a vial 820 in the receptacle 805 (if one is present) ordeliver the light to a standoff specimen at 740 (if the vial is notpresent). The receptacle 805 preferably incorporates a water tightbarrier between the interior of the receptacle and the working elementsof the probe. Windows 822 (FIG. 18) permit light to pass into and out ofreceptacle 805.

If desired, vial 820 can include a “shutter” 825 to close off the window822 adjacent to lens 800 so as to prevent stray backlight from enteringreceptacle 805 when the specimen is retained in receptacle 805.

Looking next at FIG. 19, a camera 830 may be added to the front of theprobe, with the image from the camera being displayed on the probe'sscreen 835 (FIG. 14A). With this construction, the operator can positionthe probe relative to a specimen at a standoff location 740 whilelooking at screen 835. This feature can enhance eye safety and,additionally, by providing camera magnification, can assist inpositioning the Raman pump beam at the correct location. Furthermore,the data from camera 830 can be stored, along with date and timeinformation, etc., in a removable memory chip (e.g., a CompactFlashcard) so as to permit easy documentation of a probe test.

Further Constructions

It is to be understood that the present invention is by no means limitedto the particular constructions herein disclosed and/or shown in thedrawings, but also comprises any modifications or equivalents within thescope of the invention.

1. A Raman probe comprising: a first optical fiber for receiving laserexcitation light from a light source and transmitting the same; a firstfilter for receiving light from the first optical fiber and adapted topass the laser excitation light and to block spurious signals associatedwith the light; a second filter for receiving light from the firstfilter and adapted to direct the light toward a specimen; focusingapparatus for receiving the light from the second filter, focusing thelight on the specimen so as to generate the Raman signal, and returningthe Raman signal to the second filter; wherein the second filter isfurther configured so that when the second filter receives the Ramansignal from the focusing apparatus, the second filter filters outunwanted laser excitation light before directing the Raman signal to asecond optical fiber; and a second optical fiber for receiving the Ramansignal from the second filter and transmitting the same to a lightanalyzer.
 2. A Raman probe according to claim 1 further comprising alight source.
 3. A Raman probe according to claim 2 wherein the lightsource comprises at least one 785 nm semiconductor laser with limitedlinewidth.
 4. A Raman probe according to claim 3 wherein the lightsource has a linewidth <0.2 nm FWHM.
 5. A Raman probe according to claim1 further comprising a lens disposed between the first fiber and thefirst filter for collimating light from the first fiber on the firstfilter.
 6. A Raman probe according to claim 1 wherein the spurioussignals associated with the light comprise spurious signals associatedwith the laser, the fiber, and/or both.
 7. A Raman probe according toclaim 6 wherein the spurious signals associated with the laser compriseASE.
 8. A Raman probe according to claim 1 wherein the spurious signalsassociated with the light comprise spurious signals associated with thefiber.
 9. A Raman probe according to claim 8 wherein spurious signalsassociated with the fiber comprise fluorescence.
 10. A Raman probeaccording to claim 8 wherein the spurious signals associated with thefiber comprise Raleigh and Raman scatterings.
 11. A Raman probeaccording to claim 1 wherein the spurious signals associated with thelight comprise spurious signals associated with both the laser and thefiber.
 12. A Raman probe according to claim 1 wherein the first filteris adapted to block ASE from the laser and fluorescence and Raleigh andRaman scatterings generated inside the first fiber.
 13. A Raman probeaccording to claim 1 wherein the first filter comprises a bandpassfilter.
 14. A Raman probe according to claim 13 wherein the bandpassfilter comprises a plurality of bandpass filter units working incombination with one another.
 15. A Raman probe according to claim 1wherein the first filter is adapted to filter out ASE background in theRaman domain of >300 cm−1.
 16. A Raman probe according to claim 1wherein the second filter comprises a plurality of filter units workingin combination with one another.
 17. A Raman probe according to claim 16wherein the second filter comprises three or more filter units workingin combination with one another.
 18. A Raman probe according to claim 1wherein the second filter comprises a filter unit working in combinationwith a reflector unit.
 19. A Raman probe according to claim 1 whereinthe second filter is configured at a 22.5 degree Angle of OpticalIncidence (AOI).
 20. A Raman probe according to claim 1 wherein thesecond filter is configured at a 5 degree Angle of Optical Incidence(AOI).
 21. A Raman probe according to claim 1 wherein the second filteris configured at a 10 degree Angle of Optical Incidence (AOI).
 22. ARaman probe according to claim 1 wherein the second filter comprises along-pass filter.
 23. A Raman probe according to claim 22 wherein thelong-pass filter is adapted to filter out the ASE background in theRaman domain of >300 cm−1.
 24. A Raman probe according to claim 22wherein the long-pass filter comprises a plurality of long-pass filterunits working in combination with one another.
 25. A Raman probeaccording to claim 24 wherein the long-pass filter comprises three ormore long-pass filter units working in combination with one another. 26.A Raman probe according to claim 22 wherein the long-pass filtercomprises a long-pass filter unit working in combination with areflector unit.
 27. A Raman probe according to claim 1 wherein thefocusing apparatus comprises a lens disposed between the second filterand the specimen.
 28. A Raman probe according to claim 1 wherein thefocusing apparatus comprises a first lens for receiving light from thesecond filter, a vial receptacle for receiving light from the firstlens, a second lens for receiving light from the vial receptacle, athird lens for receiving light from the second lens and focusing thatlight on a target location, whereby the focusing apparatus is adapted sothat (i) when a specimen is located in the vial receptacle, focus lighton the specimen, and (ii) when no specimen is located vial receptacle,focus light on the target location.
 29. A Raman probe according to claim28 wherein the first lens, vial receptacle, second lens, third lens andtarget location are all aligned with one another.
 30. A Raman probeaccording to claim 1 wherein the second filter is adapted to provide upto >OD10 filtration of the laser excitation light before directing theRaman signal to a second optical fiber.
 31. A Raman probe according toclaim 1 wherein a broadband reflector is disposed between second filterand the second fiber.
 32. A Raman probe according to claim 31 whereinthe broadband reflector is adapted to provide up to OD1 filtering of thelaser excitation light before directing the Raman signal to a secondoptical fiber.
 33. A Raman probe according to claim 31 wherein thebroadband reflector reflects Raman signal and passes laser excitationlight.
 34. A Raman probe according to claim 31 wherein the broadbandreflector reflects Raman signal of >300 cm−1, and passes Raman signal of0 to 300 cm−1.
 35. A Raman probe according to claim 31 wherein thebroadband reflector is configured at a 45 degree Angle of OpticalIncidence (AOI).
 36. A Raman probe according to claim 1 furthercomprising a lens disposed between the second filter and the secondfiber.
 37. A Raman probe according to claim 1 further comprising a lightanalyzer.
 38. A Raman probe according to claim 37 wherein the lightanalyzer comprises a spectrometer.
 39. A Raman probe according to claim37 wherein the light analyzer comprises a spectrometer and associatedanalysis apparatus adapted to analyze the Raman signature of thespecimen, whereby to identify the specimen.
 40. A Raman probecomprising: a light source for generating laser excitation light;focusing apparatus for receiving the laser excitation light from thelight source, focusing the laser excitation light on a specimen so as togenerate the Raman signal, and returning the Raman signal to a lightanalyzer; and a light analyzer for analyzing the Raman signature of thespecimen, whereby to identify the specimen; wherein the focusingapparatus is configured to permit the specimen to reside in a vialreceptacle or at a target location remote from the vial receptacle. 41.A Raman probe according to claim 40 wherein the vial receptacle and thetarget location are aligned with one another.
 42. A Raman probeaccording to claim 40 wherein the focusing apparatus comprises a firstlens for receiving light from the light source, a vial receptacle forreceiving light from the first lens, a second lens for receiving lightfrom the vial receptacle, a third lens for receiving light from thesecond lens and focusing that light on a target location, whereby thefocusing apparatus is adapted so that (i) when a specimen is located inthe vial receptacle, focus light on the specimen, and (ii) when nospecimen is located vial receptacle, focus light on the target location.43. A Raman probe according to claim 42 wherein the first lens, vialreceptacle, second lens, third lens and target location are all alignedwith one another.
 44. A Raman probe according to claim 42 furthercomprising a vial adapted to be seated in the vial receptacle.
 45. ARaman probe according to claim 42 wherein the vial further comprises ashutter for preventing stray backlight from entering the vial receptaclewhen the vial is disposed in the vial receptacle.
 46. A Raman probeaccording to claim 40 wherein the focusing apparatus comprises a conicalstandoff located between the vial receptacle and the target location.47. A Raman probe according to claim 46 wherein the conical standoffcomprises a window located between the vial receptacle and the targetlocation.
 48. A Raman probe according to claim 46 wherein the conicalstandoff is removably connected to the remainder of the probe.
 49. ARaman probe according to claim 46 wherein the conical standoff ispivotally connected to the remainder of the probe.
 50. A method forconducting Raman spectroscopy of a specimen, comprising: generatinglaser excitation light using a light source; passing the laserexcitation light through a first filter so as to block spurious signalsassociated with the light; directing the laser excitation light to asecond filter so as to direct the laser excitation light toward thespecimen; receiving the light from the second filter, focusing the lighton the specimen so as to generate the Raman signal, and returning theRaman signal to the second filter; wherein the second filter is furtherconfigured so that when the second filter receives the Raman signal fromthe specimen, the second filter filters out unwanted laser excitationlight; passing the filtered light received from the second filter to alight analyzer; and analyzing the Raman signature of the specimen so asto identify the specimen.
 51. A Raman probe comprising: a housing; alight source disposed within the housing for generating laser excitationlight; focusing apparatus disposed within the housing for receiving thelaser excitation light from the light source, focusing the laserexcitation light on a specimen so as to generate the Raman signal, andreturning the Raman signal to a light analyzer; and a light analyzerdisposed within the housing for analyzing the Raman signature of thespecimen, whereby to identify the specimen; wherein the focusingapparatus is configured to permit the specimen to reside at a targetlocation remote from the housing; and further comprising an opticalshield mounted to the housing so as to be disposed between the specimenand the user, whereby to optically shield the user from the lightsource.
 52. A Raman probe according to claim 51 wherein the opticalshield is adapted to block the operative wavelength of the light source.53. A Raman probe according to claim 51 wherein the optical shield has asemi-circular configuration.
 54. A Raman probe comprising: a housing; alight source disposed within the housing for generating laser excitationlight; focusing apparatus disposed within the housing for receiving thelaser excitation light from the light source, focusing the laserexcitation light on a specimen so as to generate the Raman signal, andreturning the Raman signal to a light analyzer; and a light analyzerdisposed within the housing for analyzing the Raman signature of thespecimen, whereby to identify the specimen; wherein the focusingapparatus is configured to permit the specimen to reside at a targetlocation remote from the housing; and further comprising a cameramounted to the housing so that its field of view encompasses the targetlocation, and a display mounted to the housing for displaying the imagecaptured by the camera, whereby to permit the user to position the proberelative to the specimen while watching the display.